This invention relates to char-forming aromatic polymer compositions containing active benzyl and/or allyl carbon moieties together with arylsulfonate esters.
By reason of their desirable physical properties and reasonable cost, aromatic polymers, such as polystyrene, have been used in diverse applications, e.g., as solid molding materials and as foam compositions. Unfortunately, such polymers tend to burn readily and continuously upon exposure to flame.
Aromatic polymer compositions having reduced propensity to burn have generally been prepared by incorporating therein various phosphorous-, nitrogen- and halogen-containing additives. These additives, however, often deleteriously affect the physical properties of the resulting polymeric composition. For example, the halogen-containing materials often have a plasticizing effect on the polymer composition, particularly at the elevated temperatures accompanying a fire. As a result, many aromatic polymer compositions which have been modified to be combustion resistant melt and drip readily upon exposure to flame. It has been recognized that these properties of aromatic polymers can be improved if, while burning, the aromatic polymer forms a rigid char. Such char barrier serves to enhance the structural integrity of the burning polymeric article, to inhibit dripping of molten polymer and to thermally insulate the unburned portion from the heat generated by combustion. Formation of char also reduces the smoke emission of burning polymer compositions.
It has been found that by the use of certain polymers and/or char-inducing additives, the formation of char in aromatic polymers can be induced and/or increased. See, for example, the teachings of U.S. Pat. Nos. 4,038,245 and 4,224,217. However, to date they have presented a rather limited solution in terms of polymers to which they apply and/or in terms of the types of additives involved.
In view of the aforementioned deficiencies of conventional aromatic polymers and the limited number of known char-forming compositions, it would be highly desirable to provide additional char-forming aromatic polymer compositions.